This page has been archived and is no longer updated. In honeybees or honey bees , sex is normally determined by the fertilization or non-fertilization of eggs, rather than the presence or absence of sex chromosomes. This mode of sex determination was first discovered by Johann Dzierzon, a Catholic priest, in Dzierzon reported that a virgin queen which has not taken a mating flight the queens mate only while in free flight away from nest produces only male progeny Dzierzon et al. His report was the first rigorous description of a sex determination system, occurring more than 50 years before the discovery of sex chromosomes McClung, ; Wilson, In haplodiploid systems, male progeny normally develops from unfertilized eggs, which are haploid and have just one set of chromosomes. The fertilized honey bee eggs, which are diploid and have two sets of chromosomes, differentiate into queens and worker bees.

Others are influenced by environmental conditions, such as temperature. Certain lineages appear to have flipped from genetic- to thermal-based sex determination over the course of evolutionary time, but no experimental data have shown exactly how these transitions occurred. Now, researchers have caught a real-time glimpse of a sex-determination switch in bearded dragons Pogona vitticeps native to Australia. About one-fifth of wild-caught female lizards carried the male sex chromosomes ZZ , according to a study published in Nature today July 1 , and these animals were able to mate and produce offspring whose sex was determined by the temperature at which the eggs were incubated.

Commonly, a single aphid species exhibits a wide range of reproductive strategies including cyclical parthenogenesis and obligate parthenogenesis. Sex determination in aphids is chromosomal; females have two X chromosomes, while males have one. X chromosome elimination at male production is generally random, resulting in equal representation of both X chromosomes in sons.